Expose tag and commit hash separately to user

On tables that show trees (e.g. `/tree`), we can sort and search by commit hash or tag, but the hash is only shown if the commit has no tag;

I suggest exposing both to the user (using abbreviated commit hash, probably), allowing sort by tag only (commit hash sorting is hardly useful), filtering by tagged commits, and visual verification that the displayed commit has the correct hash.

Start at the /tree table implementation and trace how commit hashes and tags are currently selected, displayed, sorted, and filtered. Check the existing table tests or UI test entry points before making changes. Done means both the abbreviated hash and tag are visible, with tag-only sorting and filtering for tagged commits.

Written by the indexing model from the issue text.